1. Field of the Invention
The present invention relates to a process system and apparatus for treating spent metal finishing effluents to recover precious metals and to remove objectionable contaminants from the effluents such as hexavalent chromium, nickel, iron, copper, cadmium, lead, zinc, silver, tin, cyanide, phosphorus species, oil and grease, surfactants, toxic organics, sludges, ashes and spent adsorbents. The process system and the apparatus of this invention represent a low cost and highly efficient alternative to present technology which requires high capital investment, and off-site disposal.
The present invention also relates to an improved method and apparatus for purifying the groundwater which has been contaminated by the objectionable contaminants listed above.
Electroplating is the production of a thin surface coating of one metal upon another by electro-deposition. This surface coating is applied to provide corrosion protection, wear or erosion resistance, anti-frictional characteristics, or for decorative purposes. The electroplating of common metals includes the processes in which ferrous or nonferrous basis material is electroplated with copper, nickel, chromium, brass, bronze, zinc, tin, lead, cadmium, iron, aluminum or combinations thereof. Precious metals electroplating includes the processes in which a ferrous or nonferrous basis material is plated with gold, silver, palladium, platinum, rhodium, indium, ruthenium, iridium, osmium, or combinations thereof. In electroplating, metal ions in either acid, alkaline or neutral solutions are reduced on cathodic surfaces. The cathodic surfaces are the workpieces being plated. The metal ions in solution are usually replenished by the dissolution of metal from anodes or small pieces contained in inert wire or metal baskets. Replenishment with metal salts is also practiced, especially for chromium plating. In this case, an inert material must be selected for the anodes. All the aforementioned substances are also the contaminants in the metal finishing effluents.
Cyanide solutions are popular for copper, zinc, brass, cadmium, silver, and gold. Non-cyanide alkaline solutions containing pyrophosphate have come into use recently for zinc and copper. Cyanides and pyrophosphates are then the contaminants if the cyanide solutions and the alkaline solutions, respectively, are used.
Electroless Plating is a chemical reduction process which depends upon the catalytic reduction of a metallic ion in an aqueous solution containing a reducing agent and the subsequent deposition of metal without the use of external electrical energy.
Electroless plating provides a uniform plating thickness on all areas of the part regardless of the configuration or geometry of the part. An electroless plate on a properly prepared surface is dense and virtually non-porous. Copper and nickel electroless plating are the most common. The basic ingredients in an electroless plating solution are: (1) A source of metal, usually a salt; (2) A reducer to reduce the metal to its base state; (3) A complexing agent to hold the metal in solution so the metal will not plate out indiscriminately; and, (4) Various buffers and other chemicals designed to maintain both stability and increase bath life. The chemistry of electroless plating is best demonstrated by examining electroless nickel plating. The source of nickel is a salt such as nickel chloride, or nickel sulfate, and the reducer is sodium hypophosphite. Accordingly, the basic ingredients in the electroless plating solutions are also the potential contaminants that must be removed from the process effluents.
There are several complexing agents can be used, the most common ones being citric and glycolic acid. Nickel ions are reduced to metallic nickel. Simultaneously, a portion of the hypophosphite anions are reduced by the active hydrogen and adsorbed on the catalytic surface producing elemental phosphorus, water and hydroxyl ions. Elemental phosphorus is bonded to or dissolved in the nickel making the reaction irreversible. Both nickel and phosphorus are produced, and the actual metal deposited is a phosphorus alloy. The phosphorus content cannot be varied to produce different characteristics in the nickel plate. The complexing agents and phosphorus compounds can not be easily removed from the waste effluents by conventional wastewater treatment processes.
Anodizing is an electrolytic oxidation process which converts the surface of the metal to an insoluble oxide. These oxide coatings provide corrosion protection, decorative surfaces, a base for painting and other coating processes, and special electrical and mechanical properties. Aluminum is the most frequently anodized material, while some magnesium and limited amounts of zinc and titanium are also treated. For aluminum parts, the formation of the oxide occurs when the parts are made anodic in dilute sulfuric acid or dilute chromic acid solutions. The oxide layer begins formation at the extreme outer surface, and as the reaction proceeds, the oxide grows into the matter. Sulfuric acid or chromic acid solutions containing the base metals are the common contaminants.
Coating operation includes chromating, phosphating, metal coloring and passivating. These coatings are applied to previously deposited metal or basis material for increased corrosion protection, lubrication, preparation of the surface for additional coatings or formulation of a special surface appearance. The contaminants produced from each of the coating operations in the below correspond to the chemicals and the base metals used in the specific coating operation.
In chromating, a portion of the base metal is converted to one of the components of the protective film formed by the coating solution. This occurs by reaction with aqueous solutions containing hexavalent chromium and active organic or inorganic compounds. Chromate coatings are most frequently applied to zinc, cadmium, aluminum, magnesium, copper, brass, bronze and silver. Most of the coatings are applied by chemical immersion, although a spray or brush treatment can be used.
Changes in the solutions can impart a wide range of colors to the coatings from colorless to iridescent yellow, brass, brown, and olive drab.
Phosphate coatings are used to provide a good base for paints and other organic coatings, to condition the surfaces for cold forming operations by providing a base for drawing compounds and lubricants, and to impart corrosion resistance to the metal surface by the coating itself or by providing a suitable base for rust-preventative oils or waxes. Phosphate conversion coatings are formed by the immersion of iron, steel, or zinc plated steel in a dilute solution of phosphoric acid plus other reagents.
Metal coloring by chemical conversion methods produces a large group of decorative finishes. This operation covers only chemical methods of coloring in which the metal surface is converted into an oxide or similar metallic compound. The most common colored finishes are used on copper, steel, zinc, and cadmium. A number of colors can be developed on zinc depending on the length of immersion in the coloring solution. Silver is given a gray color by immersion in a polysulfide solution such as ammonium polysulfide.
Passivation refers to forming a protective film on metals, particularly stainless steel and copper, by immersion in an acid solution. Stainless steel is passivated in order to dissolve any embedded iron particles and to form a thin oxide film on the surface of the metal. Typical solutions for passivating stainless steel include nitric acid and nitric acid with sodium dichromate. Copper is passivated with a solution of ammonium sulfate and copper sulfate, forming a blue-green substance on the surface of the metal.
Etching and Chemical Milling are the processes used to produce specific design configurations and tolerances or surface appearances on parts (or metal-clad plastic in the case of printed circuit boards) by controlled dissolution with chemical reagents or etchants. The spent chemical reagents or etchants are the contaminants.
Cleaning involves the removal of oil, grease and dirt from the surface of the basis material using water with or without a detergent or other dispersing agent. Alkaline cleaning (both electrolytic and non-electrolytic) and acid cleaning are both included. The contaminants from cleaning operation thus include oil, grease, dirt, detergent, dispersing agents, alkaline substances, acids, etc.
Machining is the general process of removing stock from a workpiece by forcing a cutting tool through the workpiece, removing a chip of basis material, which becomes suspended insoluble contaminant in an effluent.
Barrel Finishing or tumbling is a controlled method of processing parts to remove burrs, scale, flash, and oxides as well as to improve surface finish. Parts to be finished are placed in a rotating barrel or vibrating unit with an abrasive media, water or oil, and usually some chemical compound to assist in the operation. The spent oil, chemicals, burrs, scales, oxides, etc. are the waste substances.
Sintering is the process of forming a mechanical part from a powdered metal by fusing the particles together under pressure and heat. The temperature is maintained below the melting point of the basis metal.
Laminating is the process of adhesive bonding layers of metal, plastic, or wood to form a part.
Vapor Plating is the process of decomposition of a metal or compound upon a heated surface by reduction or decomposition of a volatile compound at a temperature below the melting point of either the deposit or the basis material.
Thermal Infusion is the process of applying a fused zinc, cadmium, or other metal coating to a ferrous workpiece by imbuing the surface of the workpiece with metal powder or dust in the presence of heat.
Salt Bath Descaling is the process of removing surface oxides or scale from a workpiece by immersion of the workpiece in a molten salt bath or a hot salt solution.
Solvent Degreasing is a process for removing oils and grease from the surfaces of a workpiece by the use of organic solvents, such as aliphatic petroleum, aromatics, oxygenated hydrocarbons, and halogenated hydrocarbons.
Vacuum Metalizing is the process of coating a workpiece with metal by flash heating metal vapor in a high-vacuum chamber containing the workpiece. The vapor condenses on all exposed surfaces.
Mechanical Plating is the process of depositing metal coatings on a workpiece via the use of a tumbling barrel, metal powder, and usually glass beads for the impacting media.
Painted Circuit Board Manufacturing involves the formation of a circuit pattern of conductive metal (usually copper) on nonconductive board materials such as plastic or glass. There are five basic steps involved in the manufacture of printed circuit boards: cleaning and surface preparation, catalyst and electroless plating, pattern printing and masking, electroplating, and etching. Other metal finishing operations include: painting, paint stripping, grinding, polishing, burnishing, deformation, shearing, heating, cutting, welding, brazing, soldering, spraying, sand blasting, coating, sputtering, assembly, calibration, testing, etc., which are self-explanatory.
The major types of effluents resulting from various metal finishing operations are: chromium bearing wastewater, cyanide bearing wastewater, oily wastewater, complexed metals bearing wastewater, precious metals bearing wastewater, common metals bearing wastewater, toxic organic bearing wastewater, solid residuals, and air emissions.
2. Description of the Prior Art
Conventional wastewater treatment technologies for metal finishing wastewater treatment include the following:
conventional sedimentation to which the influent wastewater is continuously settled by gravity, and from which the clarified supernatant is continuously discharged as the treated effluent and the settled pollutants at bottom are either continuously or periodically wasted, PA1 conventional uncovered flotation to which the influent wastewater is continuously fed, in which the floatable pollutants are continuously floated by micro gas bubbles to the water surface forming scums, and from which the clarified subnatant is continuously discharged as the treated effluent and the floated scums at top as well as air emission are continuously wasted, PA1 conventional ion exchange to which the influent wastewater is continuously fed, in which the ionic pollutants are continuously removed by the fixed bed ion exchange resins, and from which the treated effluent is continuously discharged, PA1 conventional continuous biological processes, such as activated sludge, trickling filter, rotating biological contactor, septic tank, lagoon, biological fluidized bed, etc., to which the influent wastewater is continuously fed, in which the organic pollutants are continuously consumed by the microorganisms in the presence of oxygen, and from which the wastewater is discharged to a conventional sedimentation clarifier for continuous separation of the treated effluent and the microorganisms, PA1 conventional uncovered sequencing batch reactor, to which the influent wastewater is fed intermittently, in which the microorganisms initially consume the organic pollutants when the reactor is being or has been filled by batchwise operation, and subsequently settle at bottom whenever the air supply is cut off, and from which the supernatant is discharged as the treated effluent, the gas is emitted into the air environment and the settled sludge is wasted, all by batch operation, PA1 conventional oil-water separation to which the influent wastewater is continuously fed, in which the light weight oil floats to the water surface, and from which the subnatant is continuously discharged as the treated effluent and the floated oil is wasted, and PA1 many other processes, such as reverse osmosis, ultrafiltration, microfiltration, electrodialysis, diatomaceous earth filtration, glassification, vitrification, incineration, gas phase carbon adsorption, powdered carbon adsorption, sanitary landfill, deep well injection, ocean disposal, etc. PA1 (1) the enclosed sequencing batch reactor (SBR) which with an enclosure and gas emission control means involves separate batch process steps in the sequence of filling wastewater, reacting with microorganisms, settling microorganisms and suspended solids, decanting the treated effluent, and wasting settled biological sludges in an enclosed reactor for wastewater treatment as well as for air emission control, PA1 (2) the sequencing batch sedimentation (SBS) which with or without an enclosure and gas emission control means involves separate batch process steps in the sequence of filling wastewater, reacting with chemicals and other substances, settling insoluble flocs and biomass, decanting treated effluent and wasting settled sludges and other substances, for simplified but improved wastewater or groundwater clarification, PA1 (3) the sequencing batch flotation (SBF) which with or without an enclosure and gas emission control means involves separate batch process steps in the sequence of filling wastewater, reacting with chemicals and other substances, floating lightweight insoluble flocs and biomass, discharging treated effluent, and wasting floated insoluble scums, for simplified but improved wastewater or groundwater clarification, and PA1 (4) the sequencing batch exchanger (SBE) which with an enclosure and gas emission control means involves separate batch process steps in the sequence of filling wastewater, reacting with ferrous sulfide sludge and other exchangers, settling the sludge and exchangers, decanting the treated effluent and wasting the spent ferrous sulfide and exchanger. PA1 (a) recovering precious metals in the precious metals wastewater by immersing iron in said precious metals wastewater, PA1 (b) reducing hexavalent chromium in the chromium bearing wastewater to trivalent at about pH 2.5 with sodium hydrogen sulfite or equivalent, PA1 (c) precipitating trivalent chromium, common metals, and phosphite with lime or other base at about pH 9.0-9.5, PA1 (d) oxidizing sulfite, phosphite and cyanide in cyanide bearing wastewater at pH 9.0-9.5 with an oxidant, PA1 (e) removing the complexing agents from the complexed metals wastewater with precipitating agents and adsorbents, PA1 (f) removing detergent, oil and grease from the oily wastewater with emulsion breaking agent and a pair of chemicals, PA1 (g) clarifying the combined waste above by sequencing batch sedimentation (SBS) or sequencing batch flotation (SBF), PA1 (h) final polishing the combined effluent above by adsorption with peat or sequencing batch exchanger (SBE), PA1 (i) removing toxic organics by an enclosed biological sequencing batch reactor (SBR) with air recirculation and air adsorption, PA1 (j) buffering/neutralizing each effluent or combined effluent by a neutralization filter, and PA1 (k) stabilizing all metal bearing sludges, spent adsorbents, ashes, and PCB residuals with cement or polymer solidifying agent. PA1 (a) selecting a Fill Phase which is composed of either Static Fill, or React Fill, PA1 (b) introducing said contaminated liquid to a reactor under a laminar, non-mixed environment until the reactor is totally filled, if Static Fill is chosen, PA1 (c) introducing said contaminated liquid to said reactor with chemical feeders on under turbulent environment until the reactor is totally filled, if React Fill is chosen, PA1 (d) stopping Fill Phase and starting React Phase to treat the contaminated liquid with chemicals, PA1 (e) stopping React Phase and starting Sedimentation Phase using gravity force for settling settleable and suspended solids with sufficient settling detention time, and without turbulence, PA1 (f) stopping Sedimentation Phase and starting Decant Phase for discharge of sedimentation clarified effluent (supernatant) above the reactor bottom, without disturbing the settled sludges, PA1 (g) stopping Decant Phase, and starting Sludge Discharge Phase for removal of settled sludges at the reactor bottom, PA1 (h) entering Idle Phase when there is more than one reactor or no more treatment is needed, to allow the reactor to remain idle until the reactor is ready for another cycle, and PA1 (i) repeating another cycle for liquid treatment. PA1 (a) selecting a Fill Phase which is composed of either Static Fill, or React Fill, PA1 (b) introducing said contaminated liquid to a reactor under a laminar, non-gas bubbled environment until the reactor is totally filled, if Static Fill is chosen, PA1 (c) introducing said contaminated liquid to said reactor with chemical feeders on, under turbulent environment, until the reactor is totally filled, if React Fill is chosen, PA1 (d) stopping Fill Phase and starting React Phase to treat the contaminated liquid with chemicals, PA1 (e) stopping React Phase and starting Flotation Phase using fine gas bubbles with diameters less than 80 microns for floating suspended, oily, surface-active and volatile contaminants, with sufficient floating detention time, PA1 (f) stopping Flotation Phase and starting Decant Phase for discharge of flotation clarified effluent (subnatant) near but above reactor bottom, without disturbing the floated scums on the top, PA1 (g) stopping Decant Phase and starting Sludge Discharge Phase for removal of floated scums in the reactor, as well as settleable matters at the reactor bottom, PA1 (h) entering Idle Phase when there is more than one reactor or more treatment is needed, to allow the reactor to remain idle until the reactor is ready for another cycle, and PA1 (i) repeating another cycle for liquid treatment. PA1 (a) introducing said contaminated liquid to a reactor containing reusable or freshly prepared exchanger in a Fill Phase, PA1 (b) stopping Fill Phase and starting React Phase to treat the contaminated liquid by exchanging soluble metal ions in said contaminated liquid with iron in insoluble exchanger under a mixing, turbulent environment, PA1 (c) stopping React Phase and starting Separation Phase using gravity force for settling reusable exchanger sludges and other spent exchanger sludges, without turbulence, PA1 (d) stopping Separation Phase and starting Decant Phase for discharge of exchanger purified effluent (supernatant) well above the reactor bottom, without disturbing the settled sludges, PA1 (e) deciding next phase based on the reactor's effluent quality or predetermined process operational hours, PA1 (f) if exchanger sludges are spent, not reusable, and must be discarded, stopping Decant Phase, and entering New Exchanger Phase for removal of all settled spent sludges at the reactor bottom, and addition of freshly prepared exchanger, PA1 (g) if exchanger sludges are not totally spent, and still reusable, stopping Decant Phase, and entering Idle Phase when there is more than one reactor or no more treatment is needed, to allow the reactor to remain idle until the reactor is ready for another cycle, and PA1 (h) repeating another cycle for liquid treatment. PA1 (a) starting a Fill Phase by introducing said contaminated liquid to an enclosed reactor and mixing the contaminated liquid with the pre-seeded mixed liquor containing microorganisms, with or without powdered activated carbon (PAC), in the presence of soluble gas required by the microorganisms, PA1 (b) stopping Fill Phase and starting React Phase by thoroughly bubbling the mixed contaminated liquid in said enclosed reactor for gas stripping of volatile organic compounds (VOC) and biological reduction of all organics from liquid phase, and by collecting & recycling the emitted gas stream from the enclosed reactor for gas purification and emission control, PA1 (c) stopping React Phase, and starting Sedimentation Phase under no inflow, no mixing, and no bubbling environment for one hour, to settle the microorganisms (activated sludge) and PAC if present, PA1 (d) Stopping Sedimentation Phase, and starting Decant Phase for discharge of the treated supernatant without disturbing the settled sludge blanket, PA1 (e) stopping Decant Phase and starting Sludge Discharge Phase for discharge of the excessive amount of microorganisms (activated sludge) and spent PAC, PA1 (f) entering Idle Phase in the presence of said soluble gas required by the microorganisms, when there is more than one reactor or no more treatment is needed, to allow the reactor to remain idle until the reactor is ready for another cycle, and PA1 (g) repeating another cycle for liquid treatment. PA1 (a) an inlet pipe leading a contaminated liquid to a reactor of said apparatus, PA1 (b) said reactor having the side walls, the top enclosure and the bottom thereof as an outside wall of said apparatus, PA1 (c) a chemical feeder means connected to said inlet pipe and said reactor for feeding chemicals, microorganisms, exchangers, or powdered activated carbon (PAC) slurry to said contaminated liquid, PA1 (d) mixing means inside and/or connected to said reactor for mixing the contaminated liquid with chemicals, microorganisms, PACs, or exchangers during reaction, PA1 (e) coarse bubbles distribution means inside as well as connected to said reactor for generating coarse gas bubbles (with diameter greater than 80 microns) for biological liquid treatment in the presence of microorganisms and required soluble gas, and for physical gas stripping of volatile organic compounds (VOCs) and volatile inorganic compounds (VICs) from said contaminated liquid inside said reactor, PA1 (f) fine bubbles distribution means inside as well as connected to said reactor for generating extremely fine gas bubbles (with diameter smaller than 80 microns) for dissolved gas flotation of suspended substances (including microorganisms, chemical flocs, oil, particulates, etc.) to the liquid surface inside said reactor, PA1 (g) gas moving means with gas pipe and flow meter, connected to the top enclosure of said reactor for measuring, collecting, and moving the emitted gas stream from the top of said reactor to a gas purification means, then to the bottom of said reactor, completing a cycle, PA1 (h) said gas purification means with built-in gas compressing and gas dissolving capability, connected to said gas moving means for purifying the emitted gas stream, and preparing the gas stream for recirculation to said reactor, PA1 (i) liquid discharge means connected to said reactor for discharging the treated reactor effluent, and PA1 (j) sludge discharge means connected to said reactor for discharging the sludges, spent exchangers, etc. from said reactor.
The combination of various conventional technologies is technically feasible for treatment of metal finishing effluents, but is economically unfeasible.
For instance, existing wastewater treatment methods for removing heavy metals from all metal bearing wastewaters involve chemical precipitation, conventional sedimentation, filtration, ion exchange, reverse osmosis, electrodialysis, etc. Existing treatment methods for removing toxic organics, complexing agents, detergents, oil and grease are conventional biological processes, such as activated sludge, trickling filter, rotating biological contactors, etc. All these existing methods are either inefficient or too costly. The added disadvantages of the existing treatment methods include: generation of secondary pollution (i.e. solid residuals, air emission), large land space requirement, and complication in operation.
Various wastewaters from the metal plating and finishing operations are also potential sources of pollution to groundwater. Once a groundwater source is contaminated by soluble chromium, cyanide, oil, surfactants, complexed metals, common metals, precious metals, toxic volatile organic compounds (VOCs), toxic volatile inorganic compounds (VICs), and other toxic substances, the same existing expensive wastewater treatment of the metal finishing effluents are also applied to groundwater decontamination.
Specifically, both conventional activated sludge processes and conventional uncovered sequencing batch reactor (SBR) release toxic volatile organic compounds (VOCs) into air environment, causing air pollution. Conventional coagulation/precipitation may accidentally release toxic HCN gas, sulfur dioxide gas, and fumes from its reactor under acidic conditions. All conventional processes, except conventional uncovered SBR, are continuous process units requiring separate reactors in turn, large land space. Specially trained pollution control personnel are needed for continuous process operation and monitoring.
Incineration and sanitary landfill are conventional technologies for disposal of metal bearing sludges from metal finishing operations. Incineration is energy intensive, releases toxic air emission, and produces toxic metal bearing ashes. Sanitary landfill, on the other hand, causes groundwater contamination, which is undesirable.
An efficient and cost-effective liquid treatment system for metal finishing waste streams (wastewater, air, solid residuals) and groundwater must consider the affordability, performance, precious metal recovery, waste minimization, secondary pollution elimination, and simplicity in operation. The present invention accomplishes all these objectives.
The primary objective of this invention is to disclose the improved batch processes (instead of conventional continuous processes) for treatment of metal finishing effluents. Using batch process, new or used metal finishing tanks can also be used as the wastewater treatment tanks, for space saving, cost saving, and ease of operation. The batch processes and an improved apparatus disclosed in this invention include:
Still another objective of this invention is to disclose a complete metal finishing waste treatment system for recovering precious metals by immersion technology, reducing hexavalent chromium with precise pH control and reducing agent, precipitating trivalent chromium with base at precise pH range, oxidizing sulfite, phosphite and cyanide with oxidant, removing complexing agents by chemical precipitation and adsorption, removing detergent, oil and grease with a chemical pair, removing toxic organics by an enclosed sequencing batch reactor with air emission control, clarifying the pretreated effluent by sequencing batch sedimentation or sequencing batch flotation, polishing the clarified effluent by sequencing batch exchanger, buffering/neutralizing the final effluent by a neutralization filter, and stabilizing all solid residuals by cementation or polymer solidification.
The theory and principles of the present invention are described in the section entitled "Description of the Preferred Embodiments".
A comparison between the state-of-the-art and the present invention is presented below.
The U.S. Department of Commerce, National Technical Information Service (NTIS) Report #PB 88-200,522, which was written by Lawrence K. Wang in 1984, discloses a design of continuous flotation-filtration wastewater treatment systems for a nickel and chromium plating plant. The present invention relates to a sequencing batch process and apparatus for groundwater decontamination as well as treatment of various metal plating and finishing effluents, including but not being limited to nickel and chromium plating effluents.
Proceedings of the 44th Industrial Waste Conference (p. 141-147) which is written by Larry Bonefield et al in 1990 discloses the effect of pentachlorophenol on enhanced biological phosphorus removal in conventional open-top SBR systems without enclosures. Proceedings of the 43rd Industrial Waste Conference (p. 267-274) which is written by D. V. S. Murphy et al in 1989 discloses the principles of organism selection for the degradation of glyphosate in a conventional open-top sequencing batch reactor without enclosure. The present invention adopts the enclosed sequencing batch reactor for both biological liquid treatment, physical-chemical liquid treatment and air pollution control.
Water Treatment (Volume 6, p. 127-146) written by Lawrence K. Wang in 1991 discloses the state-of-the-art continuous flotation clarifier installed in Massachusetts, U.S.A. Proceedings of the 44th Industrial Waste Conference (p. 493-504) written by Lawrence K. Wang et al in 1990 discloses the theory and principles of the state-of-the-art continuous air flotation clarification process. Proceedings of the 44th Industrial Waste Conference (p. 655-673) also written by Lawrence K. Wang et al in 1990 discloses the application of conventional continuous oil-water separation, continuous flotation clarification and conventional granular carbon adsorption. The present invention relates to the enclosed sequencing batch reactor for batch flotation clarification and batch oil-water separation.
Other conventional processes and apparatuses for wastewater treatment, groundwater decontamination, and air pollution control are described in the U.S. Pat. No. 4,789,484 to Ying et al, U.S. Pat. No. 4,859,216 to Fritsch, U.S. Pat. No. 4,892,664 to Miller, U.S. Pat. No. 4,857,198 to Meidl, and U.S. Pat. Nos. 5,049,320, 5,064,531, 5,068,031, 5,069,783, and 5,084,165 to Wang et al.
None of the aforementioned processes and apparatuses relate to the enclosed sequencing batch processes and apparatuses with built-in air pollution control capability.